The Densified Modification On Carbon Nanotube Twisted Yarn

The CNT yarn fabricated with CNTs also possesses these extraordinary mechanical properties.In addition,the macroscale,thread-like structure of the CNT yarn make it potential to be woven or knitted into fabric for practical applications,such as electric heating fabric and smart textile etc.In recent decades,three main manufacturing technique,wet spinning from CNT solutions,dry spinning from CNT arrays in vertical arrangement and direct spinning from CNT aerogels via the floating catalyst chemical vapor deposition(FCCVD)process,have been proposed to manufacture the macroscopic CNT yarn.However,There is a big gap between macroscale CNT yarn and elementary CNTs,it is because the basic component of the spun CNT yarn is the group of bundle where CNTs entangle with each other resulting in the loss of orientation,and the existing interspace between CNTs lead to weak interaction between adjacent CNTs.These defects of structure have negative effect on the properties of CNT yarn,further influence the functional performance of textile application and decrease the weavability of CNT yarn during weaving process.In order to deal with these problem and increase the potential of smart textile,in this work,the CNT film grown by floating catalyst chemical vapor deposition is twisted into cylindrical yarn.We developped a simple,effective and controllable treatment approach to densify the CNT yarn to improve its mechanical and electrical properties.To facilitate the densification and increase the properties more,we add acetone and polyvinyl alcohol(PVA)respectively during densifing process,and study the influence of acetone and polymer infiltration on the densification of CNT yarn respectively.Firstly,the CNT film was twisted to the linear twisted CNT yarn by an electric motor,and the twisted CNT yarn(CNTY)was modified into densified CNT yarn(P-CNTY).The surface morphology of CNT yarn was analyzed by scanning electron microscope(SEM)and field emission scanning electron microscope(FESEM)for big magnification.We further tested the mechanical properties and electrical properties by a XQ-2 tensile testing machine and a digital multi-meter respectively.The results showed that the twisted CNT yarn before modification possessed loose structure.However,with the compression degree increased in densification,the twisted CNT yarn is densified and oriented to the yarn axis.But overlarge compression degreewould lead to the surface damage to destory the integrity of CNT yarn and limited the improvement of performance of CNT yarn.When the D/d is 1.52,the tensile strength increased by98% with a value of 276 MPa,in the meantime,the Young's modules increased by 728% to6.458 GPa.The electrical conductivity and gauge factor were increased by 63% and 112%respectively.So this densifying method has great potentials in improving mechanical and electrical properties of CNT yarn.Secondly,in order to decrease the friction and facilitate the densification during drawing process,the twisted CNT yarn was densified under acetone infiltration(A-P-CNTY).The surface morphology,mechanical properties and electrical properties of CNT yarn was analyzed respectively.The results shown that the A-P-CNTY possessed more smooth appearance and compacted structure contrasted with P-CNTY.Therefore,we could find that the mechanical properties and electrical properties of A-P-CNTY increased more dramatically than that of P-CNTY.The tensile strength of A-P-CNTY(D/d=1.62)increased by 185% with a value of402 MPa and the Young's modules increased by 875% with a value of 7.61 GPa,respectively 46%and 18% higher than that of P-CNTY(D/d=1.52).The electrical conductivity and gauge factor of A-P-CNTY(D/d=1.62)increased by 109% and 112% respectively,15% and 91% higher than that of P-CNTY(D/d=1.52).Finally,in order to strengthen the inter-bundle interaction and orientation,the CNT film was dipping in the solution of polyvinyl alcohol(PVA),twisted into yarn(PVA-CNTY).Then the twisted yarn was densified under the PVA infiltration(PVA-P-CNTY).The surface morphology,mechanical properties and electrical properties of CNT yarn was analyzed respectively.The results shown that the PVA was coated nonuniformly and interfacial strength is poor in PVA-CNTY,influencing the improvement of properties.However,after PVA-CNTY was densified under the PVA infiltration,the polymer distributed homogeneously and interfacial strength improved in PVA-P-CNTY,And the structure of that was more compacted,oriented,and unbroken contrasted with P-CNTY.Therefore,the mechanical properties and electrical properties of PVA-P-CNTY increased more dramatically.When the D/d is up to 2.15,the tensile strength of PVA-P-CNTY increased by 960% with a value of 1.38 GPa and the Young's modules increased by 2900% with a value of 24 GPa,respectively 490% and 110% higher than that of PVA-CNTY,respectively 400%and 271% higher than that of P-CNTY(D/d=1.52).